The future of the agricultural industry in Northern Ireland depends on the ability of politicians to avoid a no-deal Brexit, a farming union has said.
The Ulster Farmers' Union (UFU) was responding to reports of a leaked UK Government document that has warned that cross-border farming trade will collapse within 24 hours of a no-deal Brexit.
However, DUP MP Sir Jeffrey Donaldson said he is unconcerned by the claims that a no-deal Brexit could trigger "consumer panic", food shortages and an increased threat in the UK within a fortnight.
He said: "We would be concerned about the veracity of this document, not only do we not know the source of it, but it also fails to take account of what the Government has stated they will put in place temporary arrangements to ensure continuing trade across the border, even if there is no deal.
"This will require reciprocity, but I can't believe the EU would want to prevent the Republic from continuing to trade with the UK.
"The UK is a big market for the agri-food sector, over 50% of Irish beef exports from the Republic go to market in Great Britain.
"We do remain hopeful that a deal will be done before the end of October."
Details of a leaked government document prepared for ministers at Westminster have been reported in recent days.
The slide, obtained by Sky News, warns the pound could fall in the first month and cross-border agriculture trade in Northern Ireland will "virtually" stop as other trade "slows".
It also said EU nationals living in the EU may start returning to Britain within a month because they will not meet EU residency rules.
While Mr Donaldson said he was not concerned by the claims, SDLP MLA Daniel McCrossan said the memo "raises significant concerns about what will happen next".
He added: "The Brexit brinkmanship now needs to change.
"The window of opportunity is closing with the October deadline fast approaching. Rather than antagonising the European Union and the Irish government, the Prime Minister and his government need to get real and realise that their path of destruction will cause many casualties - especially in the north of Ireland."
Responding to the reports, UFU president Ivor Ferguson said the organisation has continually stressed that leaving the EU without a deal will be "catastrophic for Northern Ireland's farming community".
He added: "A no-deal outcome that results in high tariffs to sell into the EU market, lower quality, cheap food imports and a hard border on the island of Ireland, remains a big concern.
"The most challenging practical issue, however, is the mitigation of single payment scheme and veterinary regulations for the export trade in agri-food goods.
"There will be huge difficulties to deliver 100% checks of accompanying health certificates, supporting documentation and risk based physical inspection of agri-food products for export using technical or administration processes."
Mr Ferguson said that any additional checks or customs facilitations between Northern Ireland and the Republic of Ireland will add time, complexity, paperwork and cost.
He added: "These practical issues will have an immediate and profound impact on farmers. Causing major disruptions to the supply chain, crippling the industry and rendering our farmers uncompetitive.
"While we accept the UK's decision to leave the EU, it is essential that we do so in a managed way.
"This should not be about giving our industry money to cope with a no deal outcome, but should instead be about securing a deal that allows trade between Northern Ireland and Great Britain as well as Northern Ireland and the Republic of Ireland to continue with minimal disruption, and also enables as frictionless as possible trade with the rest of the EU."
Mr Ferguson said the UFU will continue to lobby leading political members with the other three UK farming unions.
The UFU president added: "The future of our agriculture industry depends on our capability to reach a deal that will support the Northern Ireland farming community ahead of leaving the European Union."